City home build diary (part 1)

Meet the Mitchinsons

• Bruce and Annabel Mitchinson are in their 40s and have two children, Bailey (18) and Anthony (14). They designed their new home themselves through Bruce’s architecture firm Mitchinson Simiona Limited.
• Their new home is in Glen Innes, directly behind their previous home. They subdivided their 1000m2 property and sold the old home to make way for their new eco-friendly residence.
• The builder was Tony Dowling, from TDC Construction, and the budget for the build was $550,000.
• The green goals for the Mitchinsons were about minimising energy and water use while maintaining sunlight and outlook for their neighbours. In short, they say they aimed to take a responsible approach to urban intensification and global environmental concerns.

The site

Bruce: Our house in Glen Innes had a large section, which was great for the kids when they were growing up. In 1995 we modified the house and made it open plan which is great to keep an eye on little ones, but priorities change when they reach the teenage years. We were sort of blowing out at the seams, getting in each other’s way.

The idea was to create a home that was for a teenager family. We had a big backyard but we didn’t spend as much time there as we used to. Everyone was out doing sport on the weekends. We had a busy lifestyle. We toyed with the idea of apartment living, but we had so much stuff, like kids’ bikes and boats, it was clear that we weren’t quite at that stage.

We decided to build on the back of our section and sell the old house. The aim was to create an apartment in suburbia. However, infill housing can create some pretty miserable spaces, and the challenge was to avoid that. We decided to build the new house on the edge of the adjacent reserve, and use the reserve as our outlook.

The house we ended up building was not our first design. I’m an architect and my wife trained as an architect and we have architect friends. Together with the kids, this became a lot of ideas and opinions. The initial designs were about planning around our busy lifestyle and reaching a family consensus, which kept driving more and more complex solutions. It had to be much simpler.

Green and simple

Bruce: It was not until the third design that green initiatives became the driver. This resolved a lot of the design decisions for us.

Annabel: He’s very conscious of being green. Maybe it wasn’t so overt in the earlier designs, but still it was there. He used to read articles about sustainability in architecture and say: “Architects do that anyway. It’s a given”.

Bruce: Annabel said she wanted something ‘eloquently simple’ and the inspiration became the classic cube, a form that is prevalent in buildings constructed to the Passivhaus standard. The Passivhaus standard was formulated in Europe and is the most rigorous benchmark for energy-efficient buildings worldwide.

If you are designing a Passivhaus you have to be a certified Passivhaus designer, which I am not. My design uses some features of the Passivhaus and trades off others to suit our Kiwi lifestyle and our milder climate.

A Passivhaus has to meet strict energy criteria, with around 75-95 per cent reduction in heating energy over current energy efficiency standards. To achieve this the house must be completely airtight, and therefore a ventilation system is required to bring in fresh air. While our home has no opening windows upstairs, and is mechanically ventilated, we could not give up that seamless connection to outside living.

We wanted to open up the whole side of the house downstairs with sliding doors, and this limited the ability to create an air-tight structure. New Zealand house standards also tend to favour low-tech building materials and methods, which contributes to our unique style of green building, where the structure is able to breathe.

Our aim was to create a home that would reduce our power bill to a third of what we would normally pay.

What is a Passivhaus?

• German for ‘passive house’, it refers to a rigorous, voluntary building standard based on energy efficiency.
• Creates ultra-low energy-use buildings.
• Usually applied to new homes due to requirement for modern materials.

Bureaucracy struggles

Annabel: It was a nightmare to get from the design to breaking ground. It took years to get the approvals for the subdivision. It was taking so long, I thought it wasn’t going to happen. Lots of well-meaning friends and family said ‘give up. It’s too stressful for you all.’

After a long time tearing our hair out, I ended up going into council myself, to work alongside them to find a way through.

Bruce: By this time, we were in the recession. The plan was to do it anyway. I had decided on a builder I knew and trusted, and he was looking for work. We cleared the site, and dug the hole to get us committed and once we’d done that, there was no turning back.

Catch the next city home build diary where the Mitchinsons source green building materials.

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